Courtesy of this post, Telesto has yet again managed to decieve Bungie's coders and become bugged once more.
One of the new mods released in Season of Dawn is called Heavy Handed, which grants you half of your melee ability back when you use your melee ability, at the cost of a charge of light. However, what is important about this mod is its secondary ability, named Lock and Load. It states: While surrounded by multiple enemies, defeating an enemy with a Fusion Rifle, Shotgun, Sidearm, or Submachine Gun adds ammo for that weapon to your reserves. In order for this perk to be active, you need at least one other arc mod socketed into your armor piece.
What this interaction does with Telesto is that, while near, enemies, Every bolt not on an enemy that detonates counts as an enemy killed and will thus give you ammo for Telesto, which means infinite ammo. GG Bungie, you did it again.